New Jersey Gov. Chris Christie rejected a state-run health insurance exchange Thursday, paving the way for the federal government to step in and run one.

Christie — who was in Washington on Thursday pushing for Hurricane Sandy aid — rejected a bill passed by the Democratic state Legislature that would have built an exchange, a key part of the president’s health care law that makes available subsidies to help low- and middle-income individuals purchase coverage in new health insurance markets starting in 2014.

Echoing complaints from other Republican governors who have declined to build the key component of the president’s health law, Christie stressed unanswered questions and potential costs.

“We will comply with the Affordable Care Act but only in the most efficient and cost-effective way for New Jersey taxpayers,” he said in a statement.

But he said the federal government hasn’t told states what they need to make the assessment.

“Thus far, we lack such critical information from the federal government. I will not ask New Jerseyans to commit today to a state-based exchange when the federal government cannot tell us what it will cost, how that cost compares to other options and how much control they will give the states over this option that comes at the cost of our state’s taxpayers.”

By rejecting a state-based exchange, Christie — thought to be considering a 2016 presidential run — will please conservatives who have pressed states to resist Obamacare implementation in the aftermath of the elections. And now, New Jersey joins the growing ranks of states that will let the feds set up an exchange within their borders.

About 30 states already have signaled they’ll let the administration play a role in their exchanges, whether that means running it entirely or partnering with the states. With open enrollment scheduled to start in October, the administration has consistently assured states that they’ll be ready to run exchanges for those that refuse to do their own.

Just a handful of states that haven’t said whether they’ll run their own exchanges have until Dec. 14, and the remaining holdouts include some Republican governors who have previously expressed interest in setting up the insurance marketplaces. The undecided states include Florida, Idaho, Pennsylvania, Tennessee and Utah.

Thursday marked the second time Christie vetoed an exchange bill.

He rejected one in May, saying at the time he couldn’t decide before the Supreme Court’s health care decision and the election.

The New Jersey Legislature approved a revised exchange bill in mid-October, which forced Christie to make a decision by Thursday.

Christie said the state could run an exchange of its own in the future and noted, “The federal government has provided states with the flexibility to amend exchange selection in subsequent years.”